The present invention relates to a technique of optimizing a scan condition in a magnetic resonance apparatus.
Magnetic resonance imaging sometimes requires breath-holding of a subject as needed for the purpose of improving the signal-to-noise ratio (SNR) of magnetic resonance signals, etc. The breath-holding time is ordinarily adjusted by estimating a duration in which a subject is able to hold his/her breath from his/her age, body size, and/or the like, and taking account of the duration.
In adjusting the breath-holding time, a period of time taken for a scan, i.e., the scan time, must be changed. When the scan time should be changed, conventionally, an operator manually adjusts values of some parameters, such as the number of times of addition (number of excitations) and the repetition time.
Values of the parameters such as the number of times of addition, however, is directly related to the amount of magnetic resonance signals to be collected, which affects the SNR of magnetic resonance signals, and hence, affects image quality of a resulting image. Moreover, to secure an appropriate SNR of magnetic resonance signals, the matrix size, i.e., the resolution of an image, should be changed with the amount of change of the number of times of addition, and such a change operation must be manually performed as well. That is, currently, a situation in which values of parameters are optimized so that an image with good image quality may be obtained within a desired scan time inevitably relies upon operator's experience and/or intuition, so that an inexperienced operator may fail to stably attain good image quality or may unduly take time for adjustment. In particular, in an imaging technique of obtaining a diffusion-weighted image (DWI) that visualizes diffusive motion of water molecules inside a subject, adjustment of parameter values is highly difficult, which results in a significant tendency of the aforesaid problems.
Under such circumstances, there is a need for a technique enabling optimization of a scan condition in a magnetic resonance apparatus, particularly, parameter values for obtaining an image with good image quality within a desired scan time, to be easily and stably achieved without relying upon operator's experience and/or intuition.